Add Addressables as a direct dependency and settings, Content group entry

Cut 1 of docs/addressables-cut.md: com.unity.addressables becomes a
direct manifest dependency (was transitive via com.unity.localization),
Addressables settings are created with BuildWithPlayer forced instead of
left as a per-user preference, and Assets/Content is added to the
Default Local Group as the one folder entry Cut 2 will populate (Q1
ruling A). No code loads through Addressables yet and the folder is
empty, so this lands harmlessly on its own.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assets/AddressableAssetsData/DataBuilders/BuildScriptPackedPlayMode.asset.meta

@@ -0,0 +1,8 @@
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+guid: cad6f30924c70ae44832566c0439562d
+NativeFormatImporter:
+  externalObjects: {}
+  mainObjectFileID: 11400000
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: